Propylene polymers with improved properties

ABSTRACT

The invention relates to novel propylene polymers with improved properties especially with improved stiffness and impact strength comprising propylene homopolymers or propylene block copolymers with 90.0 to 99.9 wt % propylene and 0.1 to 10 wt % α-olefins with 2 or 4 to 18 carbon atoms, or mixtures thereof, wherein the propylene homopolymers or propylene block copolymers are β-nucleated propylene polymers, whereby the β-nucleated propylene homopolymers have an IRτ≧0.98, a tensile modulus ≧1500 MPa at +23° C. and a Charpy impact strength, ≧3 kJ/m 2  at −20° C. using notched test specimens, and the β-nucleated propylene block copolymers are polymers having an IRτ of the propylene homopolymer block of ≧0.98, a tensile modulus ≧1100 Mpa at +23° C. and a Charpy impact strength of ≧6 kJ/m 2  at −20° C. using notched test specimens. The propylene polymers with an improved property spectrum are suitable for producing molded parts in a pipe system, such as pipes and fittings, inspection chambers, pipe ducting systems, extrusion or compression molded sheets and the like.

FIELD OF THE INVENTION

[0001] The invention relates to propylene polymers with improved properties as well as to a process for producing them.

BACKGROUND OF THE INVENTION

[0002] Propylene polymer compositions from common propylene polymers and β-nucleating agents are known. β-Nucleating agents are useful in compositions for forming unstretched films which can be made porous by extraction of β-spherulites- and stretching the films (disclosed for example in U.S. Pat. No. 4,386,129; U.S. Pat. No. 4,975,469).

[0003] Another effect of β-nucleating agents in propylene compositions is the improved thermoformability. As the melting point of the 8-form of the spherulites of polypropylene based resins is generally about 144 to 148° C., contrasted with the typical melting point range of α-form spherulites of about 159 to 163° C., melt forming from these compositions is possible at lower temperatures and higher production rates (WO 93/12 262).

[0004] The disadvantage of these compositions having good impact properties is that they show unsatisfactory strength.

[0005] Conventional polypropylene homopolymers usually show high stiffness, but poor impact strength. Conventional β-nucleated polypropylenes usually have improved impact strength but also exhibit reduced stiffness.

OBJECT OF THE INVENTION

[0006] Therefore it is the object of the present invention to provide propylene polymers with improved properties characterized in having high stiffness and good impact properties simultaneously.

BRIEF DESCRIPTIONS OF THE INVENTION

[0007] According to the present invention, this object is achieved by propylene polymers with improved properties comprising propylene homopolymers with melt indices of 0.05 to 15 g/10 min at 230° C./2.16 kg or propylene block copolymers with 90.0 to 99.9 wt % propylene and 0.1 to 10 wt % α-olefins with 2 or 4 to 18 carbon atoms with melt indices of 0.05 to 20 g/10 min at 230° C./2.16 kg, or mixtures thereof, wherein the propylene homopolymers or propylene block copolymers are nucleated propylene polymers, whereby the β-nucleated propylene homopolymers have an IRτ ≧0.98, a tensile modulus of ≧1500 MPa at +23° C. and a Charpy impact strength of ≧3 kJ/m² at −20° C. using notched test specimens, and the β-nucleated propylene block copolymers are polymers having an IRτ of the propylene homopolymer block of ≧0.98, a tensile modulus of ≧1100 MPa at +23° C. and a Charpy impact strength, of 26 kJ/m² at −20° C., using notched test specimens.

DETAILED DESCRIPTION OF THE INVENTION

[0008] β-nucleated propylene polymers are isotactic propylene polymers composed of chains in a 3₁ helical conformation having an internal microstructure of β-form spherulites being composed of radial arrays of parallel stacked lamellae. This microstructure can be realized by the addition of β-nucleating agents to the melt and subsequent crystallization. The presence of the β-form can be detected through the use of wide angle X-ray diffraction (Moore, J., Polypropylene Handbook, p. 134-135, Hanser Publishers Munich 1996).

[0009] The IRτ of the propylene polymers is measured and calculated as described in EP 0 277 514 A2 on page 5 (column 7, line 53 to column 8, line 11).

[0010] According to a preferred embodiment the Enucleated propylene homopolymers or the propylene homopolymer block of the β-nucleated propylene block copolymers have an IRτ of ≧0.985. The difference of 0.005 in IRτ, IRτ being a measure for isotacticity, encompasses a significant increase in mechanical polymer properties, especially in stiffness.

[0011] The propylene homopolymers according to the present invention have melt indices of 0.05 to 15 g/10 min at 230° C./2.16 kg, preferably 0.1 to 8 g/10 min at 230° C./2.16 kg, most preferably 0.2 to 5 g/10 min at 230° C./2.16 kg.

[0012] The propylene copolymers according to the present invention have melt indices of 0.05 to 20 g/10 min at 230° C./2.16 kg, preferably 0.1 to 8 g/10 min at 230° C./2.16 kg, most preferably 0.2 to 5 g/10 min at 230° C./2.16 kg.

[0013] According to the present invention the propylene homopolymers show a tensile modulus ≧1500 MPa, preferably ≧1600 MPa and the propylene copolymers show a tensile modulus ≧1100 MPa, preferably ≧1300 MPa and most preferably ≧1500 MPa.

[0014] The propylene homopolymers according to the present invention have a Charpy impact strength of ≧3 kJ/m² at −20° C., preferably 4 to 10 kJ/m² at −20° C., most preferably 5 to 10 kJ/m² at −20° C.

[0015] The propylene copolymers according to the present invention have a Charpy impact strength of ≧6 kJ/m² at −20° C., preferably ≧9 kJ/m² at −20° C., most preferably ≧10 kJ/m² at −20° C. Charpy impact strength of up to at least 60 kJ/m² is possible for copolymers according to the invention.

[0016] According to an advantageous feature of the present invention the β-nucleated propylene polymers with an IRτ ≧0.98 being propylene polymers obtained by polymerization with a Ziegler-Natta catalyst system comprising titanium-containing solid components, an organoalumina, magnesium or titanium compound as cocatalyst and an external donor according to the formula

R_(x)R′_(y)Si(MeO)_(4-x-y),

[0017] wherein R and R′ are identical or different and are branched or cyclic aliphatic or aromatic hydrocarbon residues, and y and x independently from each other are 0 or 1, provided that x+y are 1 or 2.

[0018] Examples of propylene polymers with high IRτ obtained by polymerization with a Ziegler-Natta catalyst system, for example by slurry, bulk or gas phase polymerization, are propylene polymers as described in EP-A-0,790,262, WO 99/24,478 and WO 99/16,797.

[0019] A preferred external donor of the Ziegler-Natta catalyst system is dicyclopentyldimethoxysilane.

[0020] According to a preferred embodiment the β-nucleated propylene polymer contains 0.01 to 2.0 wt %, in each case based on the propylene polymers used, of

[0021] dicarboxylic acid derivative type diamide compounds from C₅-C₈-cycloalkyl monoamines or C₆-C₁₂-aromatic monoamines and C₅-C₈-aliphatic, C₅-C₈-cycloaliphatic or C₆-C₁₂-aromatic dicarboxylic acids, preferably N,N′-di-C₅-C₈-cycloalkyl-2,6-naphthalene dicarboxamide compounds, N,N′-di-C₅-C₈-cycloalkyl-4,4-biphenyldicarboxamide compounds, N,N′-di-C₅-C₈-cycloalkylterephthalamide compounds, N,N′-di-C₅-C₈-cycloalkyl-1,4-cyclohexanedicarbox-amide compounds and/or N,N′-di-C₆-C₁₂-aryl-C₅-C₈-diamide compounds; and/or

[0022] diamine derivative type diamide compounds from C₅-C₈-cycloalkyl monocarboxylic acids or C₆-C₁₂-aromatic monocarboxylic acids and C₅-C₈-cycloaliphatic or C₆-C₁₂-aromatic diamines, preferably N,N′-C₆-C₁₂-arylene-bis-benzamide compounds, N,N′-C₅-C₈-cycloalkyl-bis-benzamide compounds, N,N′-p-C₈-C₁₂-arylene-bis-C₅-C₈-cycloalkylcarboxamide compounds and/or N,N′-C₅-C₈-cycloalkyl-bis-cyclohexanecarboxamide compounds; and/or

[0023] amino acid derivative type diamide compounds from amidation reaction of C₅-C₈-alkyl-, C₅-C₈-cycloalkyl- or C₆-C₁₂-arylamino acids, C₅-C₈-alkyl-, C₅-C₈-cycloalkyl- or C₈-C₁₂-aromatic monocarboxylic acid chlorides and C₅-C₈-alkyl-, C₅-C₈-cycloalkyl- or C₆-C₁₂-aromatic mono-amines, preferably N-phenyl-5-(N-benzoylamino)pentaneamide and/or N-cyclohexyl-4-N-cyclohexylcarbonylamino) benzamide,

[0024] as β-nucleating agent.

[0025] Examples of N,N′-di-C₅-C₈-cycloalkyl-2,6-naphthalene dicarboxamide compounds are N,N′-dicyclohexyl-2,6-naphthalene dicarboxamide and N,N′-dicyclooctyl-2,6-naphthalene dicarboxamide.

[0026] Examples of N,N′-di-C₅-C₈-cycloalkyl-4,4-biphenyldicarboxamide compounds are N,N′-dicyclohexyl-4,4-biphenyldicarboxamide and N,N′-dicyclopentyl-4,4-biphenyldicarboxamide.

[0027] Examples of N,N′-di-C₅-C₈-cycloalkylterephthalamide compounds are N,N′-dicyclohexylterephthalamide and N,N′-dicyclopentylterephthalamide.

[0028] Examples of N,N′-di-C₅-C₈-cycloalkyl-1,4-cyclohexanedicarboxamide compounds are N,N′-dicyclohexyl-1,4-cyclohexanedicarboxamide and N,N′-dicyclohexyl-1,4-cyclopentanedicarboxamide.

[0029] Examples of N,N′-di-C₆-C₁₂-aryl-C₅-C₈-diamide compounds are N,N′-bis(p-methylphenyl)-hexanediamide, N,N′-bis(4-cyclohexylphenyl)hexanediamide, N,N′-diphenylhexanediamide, N,N′-diphenyloctanediamide and N,N′-bis(p-ethylphenyl)hexanediamide.

[0030] Examples of N,N′-C₆-C₁₂-arylene-bis-benzamide compounds are N,N′-p-phenylene-bis-benzamide and N,N′-1,5-naphthalene-bis-benzamide.

[0031] Examples of N,N′-C₅-C₈-cycloalkyl-bis-benzamide compounds are N,N′-1,4-cyclopentane-bis-benzamide and N,N′-1,4-cyclohexane-bis-benzamide.

[0032] Examples of N,N′-p-C₆-C₁₂-arylene-bis-C₅-C₈-cycloalkylcarboxamide compounds are N,N′-1,5-naphthalene-bis-cyclohexanecarboxamide and N,N′-1,4-phenylene-bis-cyclohexanecarboxamide.

[0033] Examples of N,N′-C₅-C₈-cycloalkyl-bis-cyclohexanecarboxamide compounds are N,N′-1,4-cyclopentane-bis-cyclohexanecarboxamide and N,N′-1,4-cyclohexane-bis-cyclohexanecarboxamide.

[0034] According to a further preferred embodiment the β-nucleated propylene polymer contains 0.0001 to 2.0 wt % of quinacridone type compounds, especially quinacridone, dimethylquinacridone and/or dimethoxyquinacridone; quinacridonequinone type compounds, especially quinacridonequinone, a mixed crystal of 5,12-dihydro(2,3b)acridine-7,14-dione with quino(2,3b)acridine-6,7,13,14-(5H,12H)-tetrone as disclosed in EP-B 0 177 961 and/or dimethoxyquinacridonequinone; and/or dihydroquinacridone type compounds, especially dihydroquinacridone, di-methoxydihydroquinacridone and/or dibenzodihydroquinacridone, as β-nucleating agent.

[0035] According to a further preferred embodiment the β-nucleated propylene polymer contains 0.01 to 2.0 wt % of dicarboxylic acid salts of metals from group IIa of periodic system, especially pimelic acid calcium salt and/or suberic acid calcium salt; and/or mixtures of dicarboxylic acids and salts of metals from group IIa of periodic system, as β-nucleating agent.

[0036] According to a further preferred embodiment the β-nucleated propylene polymer contains 0.01 to 2.0 wt % of salts of metals from group IIa of periodic system and imido acids of the formula

[0037] wherein x=1 to 4; R═H, —COOH, C₁-C₁₂-alkyl, C₅-C₈-cycloalkyl or C₆-C₁₂-aryl, and Y═C₁-C₁₂-alkyl, C₅-C₈-cycloalkyl or C₆-C₁₂-aryl-substituted bivalent C₆-C₁₂-aromatic residues, especially calcium salts of phthaloylglycine, hexahydrophthaloylglycine, N-phthaloylalanine and/or N-4-methylphthaloylglycine, as β-nucleating agent.

[0038] The inventive propylene polymers with improved properties may contain usual auxiliary materials such as 0.01 to 2.5 wt % stabilizers, and/or 0.01 to 1 wt % processing aids, and/or 0.1 to 1 wt % antistatic agents and/or 0.2 to 3 wt % pigments, in each case based on the propylene polymers used.

[0039] The stabilizers, contained in the inventive propylene polymers, preferably are mixtures of 0.01 to 0.6 wt % phenolic antioxidants, 0.01 to 0.6 wt % 3-arylbenzofuranones, 0.01 to 0.6 wt % processing stabilizers based on phosphites, 0.01 to 0.6 wt % high temperature stabilizers based on disulfides and thioethers and/or 0.01 to 0.8 wt % sterically hindered amines (HALS).

[0040] A further object of the present invention is a process for producing propylene polymers with an improved property spectrum from propylene homopolymers with melt indices of 0.05 to 15 g/10 min at 230° C./2.16 kg and/or block copolymers from 90.0 to 99.9 wt % of propylene and 0.1 to 10 wt % of α-olefins with 2 or 4 to 18 carbon atoms with melt indices of 0.05 to 20 g/10 min at 230° C./2.16 kg, wherein Enucleated propylene homopolymers have an IRτ ≧0.98, a tensile modulus of ≧1500 MPa at +23° C. and a Charpy impact strength of ≧3 kJ/m² at −20° C. using notched test specimens, respectively β-nucleated propylene block copolymers having an IRτ of the propylene homopolymer block of 0.98, a tensile modulus of ≧1100 MPa at +23° C. and a Charpy impact strength, ≧6 kJ/m² at −20° C. using notched test specimens, are produced by melt mixing of propylene homopolymers having an IRτ ≧0.98, respectively propylene block copolymers having an IRτ of the propylene homopolymer block of ≧0.98, with 0.0001 to 2.0 wt %, based on the polypropylenes used, of β-nucleating agents at temperatures from 175 to 250° C.

[0041] For the melt mixing of the propylene polymers and the β-nucleating agents, conventional compounding extruders are used.

[0042] In producing the inventive propylene polymers the β-nucleating agents may be introduced into the propylene polymers as master batch for example from 0.05 to 25 parts by weight of β-nucleating agent and 75 to 99.95 parts by weight of propylene polymer.

[0043] Preferred applications of the propylene polymers with improved properties as well as of mixtures with conventional propylene homopolymers and/or propylene copolymers are molded parts in a pipe system, such as pipes and fittings, inspection chambers, pipe ducting systems, extrusion or compression molded sheets and the like.

[0044] A further object of the invention is to provide articles with an improved balance of stiffness and impact strength at low temperatures.

[0045] It has been found that this object is achieved by using propylene homopolymers with melt indices of 0.05 to 15 g/10 min at 230° C./2.16 kg, which propylene homopolymers are β-nucleated, where the β-nucleated propylene homopolymers have an IRτ ≧0.98, for producing these articles. Articles with a tensile modulus of ≧1500 MPa at +23° C. and a Charpy impact strength of ≧3 kJ/m² at −20° C., using notched test specimens, can be produced by using the aforementioned propylene homopolymers.

[0046] It has been found that this object is also achieved by using propylene block copolymers with 90.0 to 99.9 wt % propylene and 0.1 to 10 wt % α-olefins with 2 or 4 to 18 carbon atoms with melt indices of 0.05 to 20 g/10 min at 230° C./2.16 kg, which propylene block copolymers are β-nucleated, where the β-nucleated propylene block copolymers have an IRτ of the propylene homopolymer block of ≧0.98, for producing these articles. Articles with a tensile modulus of ≧1100 MPa at +23° C. and a Charpy impact strength, of 26 kJ/m² at −20° C., using notched test specimens, can be produced by using the aforementioned propylene block copolymers.

EXAMPLES

[0047] The following tests were made using injection molded samples prepared according to ISO 1873

[0048] Tensile modulus according to ISO 527 (cross head speed 1 mm/min) at +23° C. Charpy impact-strength using notched specimens, according to ISO 179/1eA

Example 1

[0049] A mixture of

[0050] 90 wt % of a propylene block copolymer, obtained by combined bulk and gas phase polymerization using a Ziegler-Natta catalyst system with dicyclopentyldimethoxysilane as external donor, having an ethylene content of 8.3 wt %, an IRτ of the propylene homopolymer block of 0.98, and a melt index of 0.30 g/10 min at 230° C./2.16 kg, 10 wt % of a master batch comprising 99 parts by weight of a propylene block copolymer having an ethylene content of 8.3 wt %, an IRτ of the propylene homopolymer block of 0.985 and a melt index of 0.30 g/10 min at 230° C./2.16 kg, and 1 part by weight of pimelic acid calcium salt and 0.1 wt % calcium stearate, 0.1 wt % tetrakis[methylene(3,5-di-t-butylhy-droxyhydrocinnamate)]methane and 0.1 wt % tris-(2,4-di-t-butylphenyl)phosphite, based on the sum of the propylene polymers used, is melted in a twin screw extruder with a temperature profile of 100/145/185/210/220/200/185° C., homogenized, discharged and pelletized.

[0051] The resulting polypropylene polymer has a melt index of 0.32 g/10 min at 230° C./2.16 kg, a tensile modulus of 1290 MPa and a Charpy impact strength, notched, of 39 kJ/m² at −20° C.

Example 2

[0052] A mixture of

[0053] 94 wt % of a propylene homopolymer, obtained by bulk polymerization using a Ziegler-Natta catalyst system with dicyclopentyidimethoxysilane as external donor, having an IRτ of 0.985 and a melt index of 1.1 g/10 min at 230° C./2.16 kg, 6 wt % of a master batch comprising 98.8 parts by weight of a propylene block copolymer having an ethylene content of 8.3 wt %, an IRτ of the propylene homopolymer block of 0.985 and a melt index of 0.30 g/10 min at 230° C./2.16 kg, and 0.2 parts by weight of a mixed crystal of 5,12-dihydro(2,3b)acridine-7,14-dione with quino(2,3b)acridine-6,7,13,14-(5H,12H)-tetrone and 0.05 wt % calcium stearate, 0.1 wt % tetrakis[methylene(3,5-di-t-butylhydroxyhydrocinnamate)]methane and 0.1 wt % tris-(2,4-di-t-butyl-phenyl)-phosphite, based on the sum of the propylene polymers used is melted in a twin screw extruder with a temperature profile of 100/145/190/215/225/205/190° C., homogenized, discharged and pelletized.

[0054] The resulting polypropylene polymer has a melt index of 1.0 g/10 min at 230° C./2.16 kg, a tensile modulus of 1500 MPa and a Charpy impact strength, notched, of 11 kJ/m² at −20° C.

Example 3

[0055] A mixture of

[0056] 75 wt % of a propylene block copolymer, obtained by combined bulk and gas phase polymerization using a Ziegler-Natta catalyst system with dicyclopentyldimethoxysilane as external donor, having an ethylene content of 8.3 wt %, an IRτ of the propylene homopolymer block of 0.985 and a melt index of 0.30 g/10 min at 230° C./2.16 kg, 25 wt % of a master batch comprising 99.5 parts by weight of a propylene block copolymer having an ethylene content of 8.3 wt %, an IRτ of the propylene homopolymer block of 0.987 and a melt index of 0.30 g/10 min at 230° C./2.16 kg, and 0.5 parts by weight of hexahydrophthaloylglycine calcium salt and 0.1 wt % calcium stearate, 0.1 wt % tetrakis[methylene(3,5-di-t-butylhydroxyhydrocinnamate)]methane and 0.1 wt % tris-(2,4-di-t-butylphenyl)phosphite, based on the sum of the propylene polymers used, is melted in a twin screw extruder with a temperature profile of 100/145/185/210/220/200/185° C., homogenized, discharged and pelletized.

[0057] The resulting polypropylene polymer has a melt index of 0.32 g/10 min at 230° C./2.16 kg, a tensile modulus of 1310 MPa and a Charpy impact strength, notched, of 37 kJ/m² at −20° C.

Example 4

[0058] A mixture of

[0059] 95 wt % of a propylene homopolymer, obtained by bulk phase polymerization using a Ziegler-Natta catalyst system with dicyclopentyldimethoxysilane as external donor, having an IRτ of 0.987, and a melt index of 1.1 g/10 min at 230° C./2.16 kg, 5 wt % of a master batch comprising 97.5 parts by weight of a propylene homopolymer having an IRτ of 0.987 and a melt index of 4.2 g/10 min at 230° C./2.16 kg, and 2.5 parts by weight of N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide and 0.05 wt % calcium stearate, 0.1 wt % tetrakis[methylene(3,5-di-t-butylhydroxyhydrocinnamate)]methane and 0.1 wt % tris-(2,4-di-t-butylphenyl)-phosphite, based on the sum of the propylene polymers used, is melted in a twin screw extruder with a temperature profile of 100/145/190/215/225/205/190° C., homogenized, discharged and pelletized.

[0060] The resulting polypropylene polymer has a melt index of 1.2 g/10 min at 230° C./2.16 kg, a tensile modulus of 1765 MPa and a Charpy impact strength, notched, of 5.5 kJ/m² at −20° C.

Example 5

[0061] A mixture of

[0062] 95 wt % of a propylene homopolymer, obtained by bulk phase polymerization using a Ziegler-Natta catalyst system with dicyclopentyidimethoxysilane as external donor, having an IRτ of 0.987, and a melt index of 0.3 g/10 min at 230° C./2.16 kg, 5 wt % of a master batch comprising 97.5 parts by weight of a propylene homopolymer having an IRτ of 0.987 and a melt index of 0.3 g/10 min at 230° C./2.16 kg, and 2.5 parts by weight of N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide and 0.05 wt % calcium stearate, 0.1 wt % tetrakis[methylene(3,5-di-t-butylhydroxyhydrocinnamate)]methane and 0.1 wt % tris-(2,4-di-t-butylphenyl)-phosphite, based on the sum of the propylene polymers used, is melted in a twin screw extruder with a temperature profile of 100/145/190/215/225/205/190° C., homogenized, discharged and pelletized.

[0063] The resulting polypropylene polymer has a melt index of 0.3 g/10 min at 230° C./2.16 kg, a tensile modulus of 1750 MPa and a Charpy impact strength, notched, of 8.4 kJ/m² at −20° C. 

1) Propylene polymers with improved properties comprising propylene homopolymers with melt indices of 0.05 to 15 g/10 min at 230° C./2.16 kg or propylene block copolymers with 90.0 to 99.9 wt % propylene and 0.1 to 10 wt % α-olefins with 2 or 4 to 18 carbon atoms with melt indices of 0.05 to 20 g/10 min at 230° C./2.16 kg, or mixtures thereof, wherein the propylene homopolymers or propylene block copolymers are D-nucleated propylene polymers, whereby the β-nucleated propylene homopolymers have an IRτ ≧0.98, a tensile modulus of ≧1500 MPa at +23° C. and a Charpy impact strength of ≧3 kJ/m² at −20° C. using notched test specimens, and the β-nucleated propylene block copolymers are polymers having an IRτ of the propylene homopolymer block of ≧0.98, a tensile modulus of ≧1100 MPa at +23° C. and a Charpy impact strength, of ≧6 kJ/m² at −20° C. using notched test specimens. 2) Propylene polymers according to claim 1 comprising propylene homopolymers with melt indices of 0.1-8 g/10 min at 230° C./2.16 kg or propylene block copolymers with 90.0 to 99.9 wt % propylene and 0.1 to 10 wt % α-olefins with 2 or 4 to 18 carbon atoms with melt indices of 0.1 to 8 g/10 min at 230° C./2.16 kg, or mixtures thereof, wherein the propylene homopolymers or propylene block copolymers are β-nucleated propylene polymers, whereby the β-nucleated propylene homopolymers have an IRτ ≧0.98, a tensile modulus of ≧1600 MPa at +23° C. and a Charpy impact strength of 4 to 10 kJ/m² at −20° C. using notched test specimens, and the β-nucleated propylene block copolymers are polymers having an IRτ of the propylene homopolymer block of ≧0.98, a tensile modulus of ≧1300 MPa at +23° C. and a Charpy impact strength, of ≧9 kJ/m² at −20° C. using notched test specimens. 3) Propylene polymers according to one of the claims 1 or 2, wherein the 1-nucleated propylene homopolymers with an IRτ ≧0.98 or propylene block copolymers with an IRτ ≧0.98 in the homopolymer block are propylene polymers obtained by polymerization with a Ziegler-Natta catalyst system comprising titanium-containing solid components, an organoalumina, magnesium or titanium compound as cocatalyst and an external donor according to the formula R_(x)R′_(y)Si(MeO)_(4-x-y), wherein R and R′ are identical or different and are branched or cyclic aliphatic or aromatic hydrocarbon residues, and y and x independently from each other are 0 or 1, provided that x+y are 1 or
 2. 4) Propylene polymers according to claim 3, characterized in that the external donor is dicyclopentyldimethoxysilane. 5) Propylene polymers according to one of the claims 1 to 4, wherein the β-nucleated propylene polymer contains 0.01 to 2.0 wt %, in each case based on the propylene polymers used, of dicarboxylic acid derivative type diamide compounds from C₅-C₈-cycloalkyl monoamines or C₆-C₁₂-aromatic monoamines and C₅-C₈-aliphatic, C₅-C₈-cycloaliphatic or C₆-C₁₂-aromatic dicarboxylic acids, preferably N,N′-di-C₅-C₈-cycloalkyl-2,6-naphthalene dicarboxamide compounds, N,N′-di-C₅-C₈-cycloalkyl-4,4-biphenyldicarboxamide compounds, N,N′-di-C₅-C₈-cycloalkylterephthalamide compounds, N,N′-di-C₅-C₈-cycloalkyl-1,4-cyclohexanedicarbox-amide compounds and/or N,N′-di-C₆-C₁₂-aryl-C₅-C₈-diamide compounds; and/or diamine derivative type diamide compounds from C₅-C₈-cycloalkyl monocarboxylic acids or C₆-C₁₂-aromatic monocarboxylic acids and C₅-C₈-cycloaliphatic or C₆-C₁₂-aromatic diamines, preferably N,N′-C₆-C₁₂-arylene-bis-benzamide compounds, N,N′-C₅-C₈-cycloalkyl-bis-benzamide compounds, N,N′-p-C₆-C₁₂-arylene-bis-C₅-C₈-cycloalkylcarboxamide compounds and/or N,N′-C₅-C₈-cycloalkyl-bis-cyclohexanecarboxamide compounds; and/or amino acid derivative type diamide compounds from amidation reaction of C₅-C₈-alkyl-, C₅-C₈-cycloalkyl- or C₆-C₁₂-arylamino acids, C₅-C₈-alkyl-, C₅-C₈-cycloalkyl- or C₆-C₁₂-aromatic monocarboxylic acid chlorides and C₅-C₈-alkyl-, C₅-C₈-cycloalkyl- or C₆-C₁₂-aromatic mono-amines, preferably N-phenyl-5-(N-benzoylamino)pentaneamide and/or N-cyclohexyl-4-N-cyclohexylcarbonylamino) benzamide, as β-nucleating agent. 6) Propylene polymers according to one of the claims 1 to 4, characterized in that the β-nucleated propylene polymer contains 0.0001 to 2.0 wt % quinacridone type compounds, preferably quinacridone, dimethylquinacridone and/or dimethoxyquinacridone; quinacridonequinone type compounds, preferably quinacridonequinone, a mixed crystal of 5,12-dihydro(2,3b)acridine-7,14-dione with quino(2,3b)acridine-6,7,13,14-(5H,12H)-tetrone and/or dimethoxyquinacridonequinone; and/or dihydroquinacridone type compounds, preferably dihydroquinacridone, dimethoxydihydroquinacridone and/or dibenzodihydroquinacridone, as β-nucleating agent. 7) Propylene polymers according to one of the claims 1 to 4, characterized in that the β-nucleated propylene polymer contains 0.01 to 2.0 wt % dicarboxylic acid salts of metals from group IIa of periodic system, preferably pimelic acid calcium salt and/or suberic acid calcium salt; and/or mixtures of dicarboxylic acids and metals from group IIa of periodic system, as β-nucleating agent. 8) Propylene polymers according to one of the claims 1 to 4, characterized in that the β-nucleated propylene polymer contains 0.01 to 2.0 wt % of salts of metals from group IIa of periodic system and imido acids of the formula

wherein x=1 to 4; R═H, —COOH, C₁-C₁₂-alkyl, C₅-C₈-cycloalkyl or C₆-C₁₂-aryl, and Y═C₁-C₁₂-alkyl, C₅-C₈-cycloalkyl or C₆-C₁₂-aryl-substituted bivalent C₆-C₁₂-aromatic residues, preferably calcium salts of phthaloylglycine, hexahydrophthaloylglycine, N-phthaloylalanine and/or N-4-methylphthaloylglycine, as β-nucleating agent. 9) A process for producing propylene polymers with improved properties from propylene homopolymers with melt indices of 0.05 to 15 g/10 min at 230° C./2.16 kg and/or block copolymers from 90.0 to 99.9 wt % of propylene and 0.1 to 10 wt % of α-olefins with 2 or 4 to 18 carbon atoms with melt indices of 0.05 to 20 g/10 min at 230° C./2.16 kg, wherein β-nucleated propylene homopolymers have an IRτ ≧0.98, a tensile modulus ≧1500 MPa and a Charpy impact strength of ≧3 kJ/m² at −20° C., using notched test specimens, respectively β-nucleated propylene block copolymers having an IRτ of the propylene homopolymer block of ≧0.98, a tensile modulus ≧1100 MPa and a Charpy impact strength ≧6 kJ/m², at −20° C., using notched test specimens, are produced by melt mixing of propylene homopolymers having an IRτ ≧0.98, respectively propylene block copolymers having an IRτ of the propylene homopolymer block of ≧0.98, with 0.0001 to 2.0 wt %, based on the polypropylenes used, of β-nucleating agents at temperatures from 175 to 250° C. 10) Use of the propylene polymers with improved properties according to one of the claims 1 to 8 as well as of mixtures with conventional propylene homopolymers and/or propylene copolymers for producing molded parts in a pipe system, such as pipes and fittings, inspection chambers, pipe ducting systems, extrusion or compression molded sheets and the like. 11) Use of propylene homopolymers with melt indices of 0.05 to 15 g/10 min at 230° C./2.16 kg which propylene homopolymers are β-nucleated, where the β-nucleated propylene homopolymers have an IRτ ≧0.98, for producing articles with a tensile modulus of ≧1500 MPa at +23° C. and a Charpy impact strength of ≧3 kJ/m² at −20° C. using notched test specimens. 12) Use of propylene block copolymers with 90.0 to 99.9 wt % propylene and 0.1 to 10 wt % α-olefins with 2 or 4 to 18 carbon atoms with melt indices of 0.05 to 20 g/10 min at 230° C./2.16 kg which propylene block copolymers are β-nucleated, where the β-nucleated propylene block copolymers have an IRτ of the propylene homopolymer block of ≧0.98, for producing articles with a tensile modulus of ≧1100 MPa at +23° C. and a Charpy impact strength, of 6 kJ/m² at −20° C. using notched test specimens. 